Dentifrice preparations



in? ew United States Patent" 6 DENTIFRICE PREPARATIONS William H.'Nebergall, Bloomington, Ind., a'ssignoi-j a) Indiana'UniversityFoundation, Bloomington, Ind., a corporation of Indiana No Drawing.Application July 8, 1953 Serial No. 366,867

18 Claims. (Cl; 167-93) This invention relates to dentifricecompositions, particularly toothpastes, which, in spite of the presenceof a calcium-containing polishing agent for cleaning the teeth, arecapable of furnishing fluorides to the' teeth for their knownprophylactic function of protectingthe teeth against caries.

It has been known for some time that the presence of fluorides in verysmall amounts in the drinking water. reduces'the incidence ofcaries inthe population using such water. Even limited topical applications tothe teeth of somewhat moreconcentrated aqueous solutions of fluo ride,when made under proper conditions, have met with dramatic success in theprevention of tooth decay in children, and thispractice is apreventative measure which is generally recognized and widely usedby"'the dental profession today, I

Efforts have also been made'to provide fluorides to the teeth throughthe medium of a conventional dentifrice designed for regular'self-use inthe customary manner of practicing personal oral hygiene in the'home inconjunction "with a tooth brush, but such efforts have always. beenseverely handicapped by the tendency. for the fluoride to be inactivatedand rendered unavailableby the other ingredients of a dentifriceespecially the calcium-containing'polishing agents.

It'is' an objectof this invention to provide dentifrices suitableforhome use which, when brushedon the teeth, not only perform thecosmetic functions of cleaning. and polishing the teeth but alsoeffectively furnish fluorides in solution, readily available to the'teeth for the prophylacticfunctions of protecting the teeth againstdecay and diminishing the incidence and limiting theseverity of cariouslesions therein.

A further object of my invention is the provision of calcium-containingdental polishing agents which are more compatible with fluorides and canbe incorporated in dentifrice preparations containing fluoride. with aminimumloss of fluoride to the inactive water-insoluble form.

It is also an object of this invention to provide a method of treatingconventional calcium-containing polishing agents in order to renderthemmore compatible with the fluorides with which they are combined in agiven dentifrice.

Other objects and features of thisinvention will be ap-' parent from thedetailed description and explanation of the invention which follows.

I have discovered that the inactivation of fluorides in dentifrices 'ismost often due to the prese'nceofan incompatible polishingagent. Calciumorthophosphates, especially dicalcium-orthophosphate, are among the mostpopular of'dentifrice polishing agents for conventionaluse but have notproved suitable for use with fluorides.' I have discovered,-however,'that these. calcium'orthophosphates may be made more compatible withfluorides if theyare heat-treated in "a'certain manner prior toincorporation into the dentifrice mix.

Thus';*it has'been 'found that more of the fluorinecontaiue'd iuih'edciitifrice'miieis retained in the water-soluble 2 anti-caries activeforrn' if heat-treated calcium orthophosphates or calcium saltsjofmolecularly dehydrated phosphoric acids such as calcium pyrophosphates,calcium metaphosphates annd'calcium'polyphosphates, are used in place ofthe ordinary calcium orthophosphates. In general, it is necessary tocarry out the heat treatment of the calcium orthopho'sphates attemperatures above 200 C. and temperatures considerably above 250 C. areusu} ally preferred because the duration of treatment required toaccomplish a given improvement influoride'compati bility of a givenorthophosphate is less at the higher temperatures. The temperatureshould not be, so high as to cause incipient fusion of the phosphate,however, since additional steps would then'be required to reduce.themas's to a finely divided powder of dentifrice grade.

The exact chemical or physical'mechanism by which the calcium orthopli'osphates are mademore compatible by means of heat-treatment is onlypartially understood, but it is know'n thatflextensive changes inthesepolishing agents do occur during the course of this'heat treatment. Inthe case 'ofdicalciun'i orthophosphate and monocalciumorthophosphate'smolecular dehydration-definitely takes place and thesematerials are converted ultimately by sufficient' heat treatment intocalcium pyrophosphates, and calcium metaphosphates respectively. Thechanges which take place in the case'of-heat treating precipitatedtricalcium orthophosphates also involve the loss of tightly heldwaterfrom some source, the'eira'ct nature orcharacter of which has notbeendefinitely ascertained. I

It appears thatthe application of the name trical cium orthophosphateand theformula, ,Ca (PO to precipitatedorthopho'sphatesiswholly'inaccurate in most cases and actually ismisleading even' when the analysis of the precipitate empiricallyconforms to said formula. Al-. though such products sold' commerciallyare generally referred to in this manner or as tri-basic calciumorthophosphates and the National Formulary even describes precipitatedcalcium phosphate as Cag(PO ,it is gen erally recognized that thechemical and X-ray analysis of suchproducts generally corresponds moreclosely'to the compound known-as "hydroxylapatite- Thus, the Ca/ P ratioof such products is generallyneare r to the figure of'1.67, which istheoretical for the above formula for hydroxylapatite thanto 1;5, whichis theoretical forCa (PO However, such precipitated prod-' ucts are notabsolutely consistent either as to chemical analyses or X-ray patternsand there is not even complete. agreement among the phosphate experts asto the unique character of any given hydroxylapatite species. In fact,precipitated products I all showing-the hydroxylapatite X-ray patternbut having Ca/P ratios varying not only between 1.5 and; 1.67 butconsiderably'above l.67'have been reported. See the review Gll'lllbdSiCcalcium phos' phates by Eisenberger, Lehrman and Turner in ChemicalReviews 26, 257-96 (1940). 'Such variations in composi tion have alsobeen discussed-by many othersfsuch as Hodge, Lefevreand Bale who suggestin an, article'in the Analytical Edition of Industrial and EngineeringChemistry 10, 156-161 (1938) that the particular empirical compositionobtained may be determined by the mode of precipitation and that Ca/Pratios above1.67 may be 'ob-"' tained when precipitation occurs in thepresence of "an.

excess of calcium while Ca/P- ratios 'be1ow'1.67 may rechemical speciebut a solidisolution the compositionof= whichis continuously variableover a considerable range (Gal-IP01)";

ofn'lixturesymore alkaline thandicalcium orthophosphate The discussionofthe describes the possible variations in composition of productsincluded within the scope of the terms precipitated tricalciumorthophosphates but also helps to account for the presence in suchproducts of the rather tightly held water referred to previously. Theamount of this water, likeflthecomposition of the precipitate, isvariable but averages around 6 to 8%. This water has frequentlybeen'referred to as-water of hydration. Thus, the complete formula forthe precipitated orthophosphate has been described as Ca (PO -l-I OHowever, the in accuracy of describing this water as true water ofhydration is generally as well recognized as is the inaccuracy of the Ca(PO structure itself, because (1) the amount of this water is not aconstant percentage of the weight even for a given Ca/P ratio and (2)this water is more dificult to remove than the customary water ofhydration requiring temperatures of from 200 to-800 C. for removal. Themost, satisfactory explanation seems to be that this water content ispresent in one or more of three forms, namely 1) as OH groups in thehydroxpreceding paragraph not only 7 ylapatite lattice, (2) in Ca(OH) orH PO adsorbed or occluded within the particles of precipitatedtricalcium orthophosphate or (3) as molecular water adsorbed or occludedwithin the particles of precipitated tricalcium orthophosphate.Evidences and suggestions of the presence of these forms have beenpresented by severalworkers' including Hodge, Lefevre and Bale (seeabove), Hendricks and Hill .in Proceedings of the National Acaderny ofSciences 36, 731-737 (1950), and Posner and Stephenson in Journal ofDental Research 31, 371-382 (1952).

It is evident, therefore, that so called precipitated tricalciumorthophosphates contain a considerable amount of water which is presentneither as free moisture nor as true Water of hydration and most ofwhich requires temperature well above 200 C. for removal. This is thewater in precipitated tricalcium orthophosphates" which, whether itisadsorbed, occluded or combined, is referred to as water more tightlyheld than true water of hydration. Loss of this-water and/or changes incrystal size are the only significant changes noted on heat treatingprecipitated tricalcium orthophosphates below 700-- 800 C. However, ifthe initial empirical composition of the precipitated orthophosphate isfairly close to the formula Ca (PO the material tends to be converted bysuflicient heat treatment to .fl-tricalcium phosphate and ultimately toa-tricalcium phosphate, entirely different' crystalline forms'which canbedistinguished by means of Xrays from the initial precipitate havingthe typical hydroxylapatite X-ray pattern. If the initial empiricalcomposition of the precipitated orthophosphate is fairly close to thehydroxylapatite formula the material tends to be converted by suflicientheat treatment to oxyapatite [Ca (PO 0] which is also disting'uishableby X-rays. Bale et al. in the Analytical Edition-of Industrial andEngineering Chemistry 17, 491- 495v (1945) and MacIntire, Palmer andMarshall in Industrial and Engineering Chemistry 31, 164-169 (1945),give X-ray diffraction pattern data for these various forms of treatedand untreated calcium orthophosphates. It is possible, of course,depending upon the exact composition of the initial precipitate and theparticular heat treating cycle used, to obtain a mixture of one or moreof the several different high temperature forms referred to above In anycase, in the presence of water and especially atreduced temperatures,all,of these high temperature formstendto revert-gradually after heattreatment to' structures which show the hydroxylapatite X-ray,patternand, therefore, most of the heat-treated calcium orthophosphateswhen actually used in a dentifrice preparation will show predominantlythe hydroxylapatite pattern. i V

At the present time fluoride-compatible abrasives for use in the presentinvention are most readily obtained by heat treating conventionalcalcium orthophosphate abrasives since these latter materials arereadily available in the proper form for use in dentifrices. I havefound that the maximum increase in fluoride compatibility is obtained byheat treating said calcium orthophosphates to the point of completeconversion to the end products discussed above, namely 3- ora-tricalcium orthophosphate or calcium oxyapatite, calciumpyrophosphates and calcium metaphosphates but for the sake of avoidingadditional steps of regrinding and classifying to proper particle sizeit is preferred that fusion be avoided during heat treatment. In heattreating monocalcium orthophosphates or mixtures containing same, thepreferred temperaturesare above 200 C,.but should not exceed 900 C.;with dicalcium orthophosphates alone, temperatures from 300 to 1100 C.are most usable; while with precipitated tricalcium orthophosphatesbeneficial heat treatment may be effected at any temperature'from 300 to1500 C. although almost never is there an additional advantage to begained in heating the material above 13001400 C. and generallytemperatures above 1000 to 1100 C. would not be pre ferred. It should beremembered that when mixtures of the above species or when mixed saltscontaining other metal cations in addition to calcium aretreated, thefusion temperatures will tend to be lowered and restriction oftemperatures to the upper limits given above can not be strictly reliedupon to avoid incipient fusion.

It should also be pointed out that the above described end productsthemselves, i. e. 5- and a-tricalcium orthophosphates, calciumoxyapatites, calcium pyrophosphates, and calcium metaphosphates or anydistinctly characterized intermediate products such as calciumtriphosphate' (Ca P O- or other polyphosphates or mixtures of any ofthese, regardless of whether they have been prepared by heat-treatmentdirectly from the corresponding conventional calcium orthophosphates, orby precipitation from other salts or from the molecularly dehydratedacids, orotherwise, may be used, in the appropriate range of particlesizes,.as the fluoride-compatible abrasives'of the present invention. Asused in the claims the term calcium metaphosphate refers to a monomericcompound represented by the formula Ca(PO and the term calciumpolyphosphates refers to polymeric calcium phosphates, whether in theform of rings or straight chains, and includes calcium pyrophosphate(calcium dipolyphosphate). Although straight calcium salts are pre-'ferred, mixed salts containing both calcium and other metal cations inaddition are also included within the scope of this invention.

The following specific examples illustrate some procedures which can befollowed in preparing my fluoridecompatible polishing agents.

Example I most entirely converted to calcium pyrophosphate The improvedcompatibility of this material.

( 2 5 7)- towards fiuoride is illustrated by the following experiments:

0.85, g. samples of the abrasive before and after heat treatment wereshaken for a period of 5 hours with 25 g ml. portions of a solutioncontaining 1000 p. p. m. of

'5 centrifuged and aliquots of the appropriate size} t0' (;0 'l-'no-morethan 50 micrograms of original fluorine were taken of the clearsupernatant liquid after centrifugation. The samples were analyzed forfluorine by means of the well known Willard and Winter procedure whichincludes distillation in the presence of perchloric acid and titrationof the distillates against thorium nitrate in the presence of alizarinsulfonate. Hydroxylamine hydrochloride and sodium chloride were added tothe distillates before the titrations in accordance with therecommendation of H. A. Williams in the Analyst 71, 175 (1946).

In this manner it was found that 59% of the fluoride originally presentwas still in solution in the sample shaken with the heat-treatedabrasive while only 5.6% of the original fluoride was left in thesolution shaken with the untreated abrasive.

Instead of heating at a temperature of 815 C. for one (1) hour as in theabove example, substantially the same beneficial results can be securedby heating for 6 hours at 400 C.

Substantially the same results can be obtained if either calciumtriphosphate or a mixed salt such as calcium sodium pyrophosphate (CaNaP O is substituted for the heat-treated abrasive in the preceding test.

Dentifrice grade dicalcium orthophosphate dihydrate usually contains afraction of a percent of a stabilizer, .such as Na4PzO7 or M g (PO addedfor the purpose of preventing loss of water of hydration during longtimestorage at climatic temperatures. However, in the above example it isimmaterial whether these stabilizers are present, and dicalciumorthophosphate dihydrate containing either, both, or neither of thesestabilizers, or even anhydrous dicalcium orthophosphate could besubstituted as starting materials in the above experiments withoutnullifying the beneficial effects of the heat treatment. Anhydrousdicalcium orthophosphate' is not appreciably more compatiblewith-fluoride ion than is the corresponding dihydrate, and heattreatment which is suflicient only to remove water of hydration is ofvery little benefit.

Example II A quantity of powdered monocalcium orthophosphate monohydratespread in a uniform layer on a clean, un-' reactive heat-resistantsurface is placed in an oven heated to a uniform and constanttemperature of 650 C. After Zhours at this temperature the treatedmaterial is found to be almost completely converted to calciummetaphosphate and much more compatible with fluorides than formerly asshown by the following experiment.

The fluoride compatibility of this heat-treated phosphate was comparedwith that of the untreated monocalcium orthophosphate monohydrate by thesame procedure used in Example I. In this Way it was found that all ofthe original fluoride remained in the solution which had been in contactwith the heat-treated phosphate while only about 5% of the originalfluoride was left in the solution which had contacted the untreatedabrasive.

Example III Precipitated dentifrice grade tricalcium orthophosphatemeeting specifications set out by the National Formulary is subjected toa temperature of 815 C. for -1 hour. The treated material is found to begreatly improved over the original tricalcium phosphate with respect tofluoride-compatibility as shown by the figures obtained on availablefluoride remaining in a solution originally 1000 p. p. m. in fluorine(as SnF after contacting samples of same with measured quantities of therespective abrasives. These. figures were 50% available from the heattreated material but only 12% from ,the control. Such moderate heattreatment does not produce a preferred abrasive of this invention.

If .the .heat treatment of .the original precipitated dentifrice gradetricalcium orthophosphate is continued {or 2 hours or more at anytemperature above about 900 C., the loss of water is almostcompleted.and the tricalcium orthophosphate is converted almost entirely to theB-form or to calcium oxyapatite or mixtures of the two. Continuedheating to temperatures above 1115 C. will generally resultinappreciable conversion of any it-tricalcium phosphate to the a-form,sometimes called 'y-phase. These phase changes are discussed in thereview by Eisenberger, Lehrman and Turner mentioned before.

The above examples, which describe the simplest form of dentifricecomposition contemplated by the present invention, i. e. the simplemixture of abrasive and fluoride, demonstrate most directly and clearlythe improve ment in fluoride-compatibility of the specially heat-treatedcalcium orthophosphates or molecularly dehydrated calciumorthophosphates over the conventional calcium orthophosphate dentifriceabrasives. The additional. ex..- amples which follow illustrate in moredetail some of the finished dentifrice compositions which can beprepared by the use of abrasives of the class which I have discovered tobe more compatible with fluorides than are the conventional dentifriceabrasives, which class includes such well-characterized chemical speciesas calcium pyrophosphates, calcium polyphosphates, calciummetaphosphates, 3-v and tat-tricalcium orthophosphates and calciumoxyapatite. These additional examples will also serve to indicate someof the preferred conditions for the preparation and use of suchdentifrice preparations.

Example IV Some of the calcium pyrophosphate prepared. in Ex ample I byheating dicalcium orthophosphate dihydrate for one hour at a temperatureof 815 C. was used in making a fluoride-containing toothpaste of thefollowing composition:

Parts by weight Heat-treated CaHPO -2H O 41.6 Synthetic detergent 1.4Glycerin'e 25.0 Water 28.0 Irishmoss extract 1.5 Stannous fluoride 1.6Flavorings 0.9

Total 100.0

The procedure for preparing the toothpaste of the above composition wasas follows:

The Irish moss extract was wet out in part of the glycerine and thecalcium pyrophosphate was wet out in part of the water, in which thesynthetic detergent had been dissolved. These slurries were thenmixed'together with heating until a uniform temperature of C. wasreached. The thickened paste mixture was then cooled to a temperature of35 C. and the flavoring, the remaining glycerine and the remaining watercontaining the stannous fluoride were all added and mixed in tho:-oughly to give a homogeneous paste of suitable consistency.

This paste was then compared for its ability to release fluoride insolution with a similar product of the same composition with the oneexception that untreated dicalcium orthophosphate was .used as theabrasive instead of the heat-treated material which had been convertedlargely to pyrophosphate by the heat-treatment The comparison test wasmade by analyses of the supernatant liquid phases obtained from slurriesof the pastes in water.

The analytical technique was as follows:

Slurries were made :by shaking 15 g. of the dentifrice with 45 g. ofwater in ml. screw cap glass bottles for 30 minutes. The liquid phasewas withdrawn after most of the solid matter had settled out and wascentrifuged at 15,000 R. P. M. for 1 hourin order to separate out theremaining solids. Aliquots of the appropriate size to contain no morethan 50 micrograms of fluoride were taken of the clear supernatantliquid phases and added to 1 g. of samples of calcium oxide. Thesemixtures were then evaporated to dryness and ignited to remove organicmatter. Then the available fluoride content was determined by theWilliams modification of the Willard and Winter perchloric aciddistillation and thorium nitrate titration, just as for the tests on theabrasives alone, as described in Example I above.

In this manner it was determined that about 16% of the total fluoridecontent originally added to the paste was available in water-solubleanti-caries active form in the paste made from the heat-treated abrasivewhile only about 8% of the total fluoride was available in the controlpaste. In a similar paste made with anhydrous dicalcium orthophosphateonly 6% of the original fluoride was found in' the supernatant liquidobtained from its slurry.

The greater effectiveness of the fluoride dentifrices prepared with myheat-treated abrasives in protecting the teeth against attack by acidsand the carious process has also been demonstrated by extensive acidsolubility studies on tooth enamel (both whole and powdered) before andafter treatment with slurries of the test dentifrices described in thisand the following examples.

The improved effectiveness of fluorine-containing compounds whichnormally dissociate to yield fluoride ions (F-) in aqueous solution whenused in dentfrices containing calcium pyrophosphate or any otherheat-treated calcium orthophosphate in place of conventional calciumorthophosphates can be readily noted with pastes containing anyconcentration of fluoride-producing fluorine from 100 p. p. m. on upinstead of the 1.6% stannous fluoride used-above, whichis equivalent to4000 p. p. m. P. However, a limit of 4000 p. p. m. of fluorineistentatively made for reasons of safety in avoiding any possibility offluorine toxicity from the regular use of such dcntifrices. This safetylimit is figured on the improbable assumption that all of the fluoridein the average amount of paste used by ahuman-being over any givenperiod of time would actually be ingested. Thus, this'limit is obviously'very' conservative. All things considered, the preferredconcentrationis about 0.1% fluoride-producing fluorine (or about 0.4%stannous fluoride) which is equivalent to about 1000 p. p. In. F. In anycase it is believed that there would seldom be any significantadditional. advantage in using more than 1% fluoride-producing fluorine($10,000 p. p. m.) in the composition of the present inventionregardless of toxicity questions, which have not yet been fully settledfor products of this .type. These fluorine concentrations may befurnished in the form of any non-toxic fluorine-containing compounds,which normally dissociate in aqueous solution to yield fluoride ionsincluding fluorides such .as

NaF, SnF- ZnF SnF can, NH4F, KF, LiF, CrF

the more complex fluorine-containing salts of the same metals or ammoniasuch as the fluosilicates e. g. Na SiF and also fluotitanates etc., aswell as mixed halides such as chlorofluorides of the same metals orammonia, -e. g. SnClF.

- Substitutions can be made freely with respect to all the beneficialresults obtained by the practice of this invention. Thus sorbitols,glycols, or silicones may be used compatible calcium phosphatecompounds. Gum tragacanth and other natural gums, or alginates and othermucilaginons vegetable extracts of land or sea origin may be used inplace of the Irish moss extract. And, of course, wide .freedom of choiceis possible in selecting the detergents and flavorings to be used. Anyother additional ingredients suitable for dentifrice use which arecompatible with the particular fluorine compounds employed may also beused. No special problems are introduced by the use of calciumpyrophosphate or my other heat treated calcium orthophosphates sincethey are even less reactive and therefore more stable and compatible notonly with the fluorides but also with almost any other possibledentifrice ingredient than are the more conventional polishing agentssuch as dicalcium orthophosphate, precipitated tricalciumorthophosphatc, etc.

Additional specific examples of dentifrice compositions preparedaccording to the teachings of this invention are the following.

Example V A commercial sample of calcium pyrophosphate. pre

pared in proper form (particle size, softness, etc. for dentifrice usewas incorporated in a fluoride-containing tooth paste of the followingcomposition:

Parts by weight The process of preparing this paste was as follows: Thegum tragacanth was wet out in part of the glycerine; the syntheticdetergent and the sodium fluoride remaining ingredients of these pasteswithout affecting the were dissolved in the water and the remainingglycerine added to this solution. The pyrophosphate was then wet out inthe aqueous mixture and this slurry was then mixed with the gumtragacanth slurry and the combined mass was heated to C. and cooled to32 C. while being mixed continuously. Finally the flavor was added andmixed in thoroughly to give a homogeneous finished paste product. Thesuperiority of this toothpaste over a similar product containing thesame amount of fluoride but with dicalcium orthophosphate dihydrate asthe abbrasive can be seen from the following results of analyses foravailable fluoride in slurries of the two products. These analyses werecarried out according to the procedure described in Example IV above andshowed about 36% of the original fluorine in available form in thepyrophosphate paste compared toonly 3% in the control paste.

In order to secure the beneficial effects of the dentifrice compositionsof my invention on the teeth it is only necessary to apply theseproducts to the various tooth surfaces by means of a brush much in theusual manner of practicing oral hygiene in the home. In order to obtainthe maximum benefits from the use of these products they should beapplied in the greatest possible strength as thoroughly as possible toall of the tooth surfaces which can be reached. A paste-form product ispreferred since this type of dentifrice is easiest to handle on a brushand apply to the teeth without adding moisture other than that in themouth and at the same time the available fluoride-content in a pastedentifrice is already dissolved and ready for immediate activity on thetooth surfaces.

Example VI The heat-treated monocalcium orthophosphate prepared inExample 11 by heating conventional monocalcium orthophosphate for 2hours at 650 C. was used in making a fluoride-containing powderdentifrice according to the following formulation:

Parts by weight Heat-treated monocalcium orthophosphate (from Theavailable fluoride in a slurry of this dentifrice was determined by thesame procedure described in connection with the analyses of Example IVand was found to be 100% of that added as SnF In contrast, a similartooth powder prepared with unheat-treated monocalcium orthophosphateyielded only 49% of its total fluoride in available form when analyzedin the same way.

Use of a commercial calcium metaphosphate in the above toothpowderformula considerably increased the amount of available fluoride overthat of the control powder containing monocalcium orthophosphate thoughnot to the level of 100% as found in the product made with heat-treatedmonocalcium orthophosphate.

It is obvious that the above examples are illustrative only of the manypossible variations of which my invention is susceptible and in no wayexhaustive of the innumerable combinations of fluorine-containingingredients and heat-treated calcium orthophosphate polishing agentswhich it is possible to use in gaining the beneficial results of myinvention. Accordingly the scope of my invention should not be limitedby the above examples but only to the composition ranges specified inthe following claims. As used herein the term calcium orthophosphatesshall be understood to apply generally to all of the known andrecognized species which can be formed by precipitation of mixing Ca++ions and P ions in aqueous solution, whether in the presence or absenceof other metal cations, including specifically the hydroxylapatitestructure and mixed salts containing both calcium and other metalcations.

What I claim as new and desire to protect by United States LettersPatent is:

1. A dentifrice combining a fluorine-containing compound and anabrasive, in which said fluorine-containing compound is one whichnormally dissociates to yield fluo ride ions in aqueous solution, andwhich is present in said dentifrice in an amount which contains at least0.01%, by weight, of ionizable fluoride but not more than 0.4%,

by weight, total fluorine, and in which said abrasive is present as atleast 20%, by weight, of said'dentifrice and comprises essentially atleast one material selected from the group consisting of calciumpolyphosphates, calcium metaphosphate, calcium oxyapatite, and panda-tricalcium orthophosphates.

2. The dentifrice of claim 1 in which the fluorine-containing compoundin stannous fluoride and the calcium polyphosphate is calciumpyrophosphate.

3. The dentifrice of claim 1 in which the fluorine-containing compoundis sodium fluoride and the calcium polyphosphate is calciumpyrophosphate.

4. The dentifrice of claim 1 in which the fluorine-containing compoundis stannous fluoride and the abrasive comprises essentially calciummetaphosphate. I

5. The dentifrice of claim 1 in which the fluorine-containing compoundis sodium fluoride and the abrasive comprises essentially calciummetaphosphate.

6. The dentifrice of claim 1 in which the fluorine-containing compoundis stannous fluoride and the abrasive comprises essentiallyfi-tricalcium orthophosphate.

7. The dentifrice of claim 1 in which the fluorine-containing compoundis sodium fluoride and the abrasive comprises essentially ,B-tricalciumorthophosphate.

8. The dentifrice of claim 1 in which the fluorine-con- 10 tainingcompound is sodium fluoride and the abrasive comprises essentiallycalcium triphosphate.

9. The dentifrice of claim 1 in which the fluorinecontaining compound isstannous fluoride and the abrasive comprises essentially calciumtriphosphate.

10. The dentifrice of claim 1 in which the fluorinecontaining compoundis stannous fluoride and the abrasive comprises essentially calciumpolyphosphate.

11. The dentifrice according to claim 1 in which the fluorine-containingcompound is sodium fluoride and the abrasive comprises essentiallycalcium polyphosphate.

12. A toothpaste combining a fluorine-containing compound and anabrasive, in which said fluorine-containing compound is one whichnormally dissociates to yield fluoride ions in aqueous solution andwhich is present in said dentifrice in an amount which contains at least0.01%, by weight, of ionizable fluoride but not more than 0.4%, byweight, of total fluorine, and in which said abrasive is present as from20% to 60%, by weight, of said dentifrice and comprises essentially atleast one material selected from the group consisting of calciumpolyphosphates, calcium metaphosphate, calcium oxyapatite, and B- and utricalcium orthophosphates.

13. The toothpaste of claim 12 in which the fluorinecontaining compoundis stannous fluoride.

14. The toothpaste of claim 13 in which the calcium polyphosphate iscalcium pyrophosphate.

15. The toothpaste of claim 12 in which the fluorinecontaining compoundis sodium fluoride.

16. The toothpaste of claim 15 in which the calcium polyphosphate iscalcium pyrophosphate.

17. A toothpaste comprising by weight from about 10% to 40% of water,from about 10% to 40% glycerine, stannous fluoride in an amountequivalent to 0.01% to 0.4% of fluorine, and from about 20% to 60% ofcalcium pyrophosphate.

18. A toothpaste comprising by weight from about 10% to 40% of water,from about 10% to 40% of glycerine, sodium fluoride in an amountequivalent to 0.01% to 0.4% of fluorine and from about 20% to 60% ofcalcium pyrophosphate.

References Cited in the file of this patent UNITED STATES PATENTS2,018,410 McDonald Oct. 22, 1935 2,191,199 Hall Feb. 20, 1940 2,272,617Cox Feb. 10, 1942 2,589,272 Miller Mar. 18, 1952 2,636,806 Winter Apr.28, 1953 2,700,012 Merckell Jan. 18, 1955 FOREIGN PATENTS 644,339 GreatBritain Oct. 11, 1950 644,360 Great Britain Oct. 11, 1950 572,352 GreatBritain Oct. 3, 1945 3,034 Great Britain of 1914 OTHER REFERENCES Drugand Cos. Ind. (61:5), November 1947, Fluorine and the Teeth, pp.611-613, 696-700.

J. Am. Pharm. Assn., May 1948, pp. 314 and 316.

Phillips; J. Am. Dent. Asso., vol. 40, No. 5, May 1950, pp. 513-519.

Bibby: J. Am. Dent. Asso., vol 34, January 1947, pp. 26-32.

Wadwani: Current Sci. of India, November 1951, pp.

Smith: Publ. of the Am. Asso., for the Advancement of Sci., No. 19,1942, Fluorine and Dental Health, pp. 12-22.

MacIntire: Ind. and Eng. Chem., February 1938, vol. 30, No. 2, pp. -162.

McClendon: A reprint from J. Dental Res., vol. 26,

No. 3, June 1947, pp. 233-239.

1. A DENTIFRICE COMBINING A FLUORINE-CONTAINING COMPOUND AND ANABRASIVE, IN WHICH SAID FLUORINE-CONTAINING COMPOUND IS ONE WHICHNORMALLY DISSOCIATES TO YIELD FLUORIDE IONS IN AQUEOUS SOLUTION, ANDWHICH IS PRESENT IN SAID DENTIFRICE IN AN AMOUNT WHICH CONTAINS AT LEAST0.01%, BY WEIGHT, OF IONIZABLE FLUORIDE BUT NOT MORE THAN 0.4%, BYWEIGHT, TOTAL FLUORINE, AND IN WHICH SAID ABRASIVE IS PRESENT AS ATLEAST 20%, BY WEIGHT, OF SAID DENTIFRICE AND COMPRISES ESSENTIALLY ATLEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF CALCIUMPOLYPHOSPHATES, CALCIUM METAPHOSPHATE, CALCIUM OXYAPATITE, AND B- ANDA-TRICALCIUM ORTHOPHOSPHATES.